Section 15. A surety upon the bond of a pilot desiring to be discharged from liability thereon shall give notice thereof to the commissioners, and shall also give written notice to such pilot, which may be served by a constable, and shall, with the return of the constable thereon, be filed with the state treasurer, and at the expiration of thirty days therefrom, the liability of such surety for the subsequent acts of said pilot shall cease. If a pilot so notified fails to furnish a new bond before the expiration of said thirty days, his commission shall be void.